M340L Exam 3A - Linear Algebra - Prof. Arlo W. Schurle, Exams of Mathematics

The fall, 2009 exam 3a for the m340l linear algebra course. It includes instructions, 8 problems, and scoring rubrics for students. The problems cover topics such as eigenvalues, eigenvectors, diagonalizability, linear transformations, and orthogonal bases.

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Pre 2010

Uploaded on 05/23/2010

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M340L EXAM 3A 2:00
FALL, 2009
Dr. Schurle
Your name:
Your UTEID:
Show all your work on these pages. Be organized and neat. Your work should be your
own; there should be no talking, reading notes, checking laptops, using cellphones, .. . .
1. (10 points) Explain in detail why eigenvalues of a matrix Amust be solutions of
det(AλI) = 0.
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M340L EXAM 3A 2:

FALL, 2009

Dr. Schurle

Your name:

Your UTEID:

Show all your work on these pages. Be organized and neat. Your work should be your own; there should be no talking, reading notes, checking laptops, using cellphones,....

  1. (10 points) Explain in detail why eigenvalues of a matrix A must be solutions of det(A − λI) = 0.

YOUR SCORE: /

  1. (10 points) Explain in detail why a p × p matrix A is diagonalizable exactly when there is a basis for Rp^ consisting of eigenvectors of A.
  2. (10 points) Is 6 an eigenvalue of the matrix

  

  ? If so, find a basis

for its eigenspace. If not, justify your answer.

  1. Let V be a vector space with basis B = {b 1 , b 2 }. Suppose that T : R^3 → V is a linear transformation such that

T

 

 

 

  = 5b 1 −^2 b 2 and^ T

 

 

 

  = 2b 1 +^ b 2 and^ T

 

 

 

  = b 1 + 4b 2.

(a) (6 points) Calculate and simplify T

 

 

 

 .

(b) (6 points) What is the matrix for T relative to the standard basis for R^3 and the basis B for V?

(c) (6 points) Suppose C is another basis for V , where

c 1 = 5b 1 + 2b 2 ,

c 2 = 7b 1 + 3b 2. What is the matrix for T relative to the standard basis for R^3 and the basis C for V?

  1. Let W be the subspace of R^4 spanned by the vectors u 1 , u 2 , u 3 , where

u 1 =

  

   , u 2 =

  

   , u 3 =

  

  .

(a) (4 points) Verify that {u 1 , u 2 , u 3 } is an orthogonal basis for W.

(b) (10 pts.) Write y =

  

   as the sum of a vector in W and a vector in W ⊥.

(c) (4 points) Find the distance from y to the subspace W.

(d) (6 points) Find a basis for W ⊥.